Cause

inSync cannot copy/delete/rename any path name longer than 256 characters.

The name of the folder, including folder path, which inSync needs Read/Write access to, is no longer than 256 characters.

This is not a limitation on the inSync side, but a limitation of Win32 API library which inSync uses to access Windows directories and files. Standard Windows applications like Windows Explorer do not work directly with such long file or folder names. When these applications attempt Read/Write operations on a folder, Windows includes the entire path, starting with the drive label, ending with the last subfolder and the file name itself.

Resolution

Rename the folder or file name and move it to another location to make sure the complete folder path does not exceed the 256-character limit.

See also

For more information on the folder path limitations in Windows, see this article from Microsoft.